196 THE VOYAGE OF H.M.S. CHALLENGER. 



Dimensions. Diameter of the outer shell 012, middle O06, inner 0'03 ; cortical pores 0'012, 

 bars 0-003 ; length of the six spines 0'08, breadth 0'03. 



Habitat. Central Pacific, Station 266, depth 2750 fathoms. 



14. Hexacontium hexaconicum, n. sp. 



Cortical shell spiny, thick walled. Pores regular circular, of the same breadth as the bars, ten 

 to twelve on the radius ; between them long bristle-shaped by-spines, half as long as the six main 

 spines. Eadial proportion of the three spheres = 1:3:9. Six main spines conical, as long as the 

 radius of the outer shell, four times as broad at the base as one pore. 



Dimensions. Diameter of the outer shell 018, middle 0'06, inner 0'02 ; cortical pores and bars 

 0'005 ; length of the spines 01, basal breadth 0'02. 



Habitat. Antarctic Sea, Station 157, depth 1950 fathoms. 



15. Hexacontium asteracanthion, Haeckel. 



Haliomma asteracanthion, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, 



p. 816. 

 Adinomma asteracanthion, Haeckel, 1862, Monogr. d. Kadiol., p. 441, Taf. xxiii. figs. 5, 6. 



Cortical shell thin walled, spiny ; its pores circular, without hexagonal frame (as a rule very 

 regular, but in other specimens more or less irregular), often very variable in size, three to six times 

 as broad as the bars, commonly seven to eight on the radius. Eadial proportion of the three 

 spheres = 1:2:4, or sometimes 1:3:8. Pores of the two inner shells also circular, but much 

 smaller ; those of the middle shell about half as broad, those of the inner shell one-fourth to one- 

 sixth as broad as the pores of the outer shell. Six radial spines strong, three-sided prismatic, 

 about as long as (or somewhat longer than) the radius of the outer shell, as broad as one of its 

 large meshes. Accessory spines very numerous and very thin, bristle-like, usually half as long as 

 the six main spines. (For the variability of this common species compare my Monograph, p. 442.) 



Dimensions. Diameter of the outer shell 01 to 012, of the middle 0'04 to OD6, of the inner 

 0-02 to 0-03 ; cortical pores 0'005 to O'Ol ; length of the six spines 0'06 to O'OS. 



Habitat. Cosmopolitan; Mediterranean, Atlantic, Pacific, surface. 



Subgenus 3. Hexacontosa, Haeckel. 



Definition. Pores of the cortical shell irregular, of different size or form ; surface 

 smooth, without radial by-spines or papillae (other than the six main spines). 







16. Hexacontium axophcenum, n. sp. 



Cortical shell thin walled, smooth. Pores irregular polygonal, three to nine times as broad as 

 the bars ; seven to ten on the radius. Eadial proportion of the three spheres = 1:3:8. Both 



